1. Field of the Invention
The invention pertains to the field of document scanners. Specifically, the present invention relates to scanners for documents having some form of conductive indicia embedded, imprinted or affixed thereon.
2. Description of the Related Art
The sale of lottery tickets is a multi-billion dollar a year business. These tickets are nearly universally available in grocery stores, convenience stores and countless other venues. They provide inexpensive and safe opportunities for consumers to spend a small amount of money in exchange for a chance to win goods, services or cash. Moreover, the sale of lottery tickets often benefits the local community by providing a welcome additional source of funding for education and health programs, among others.
One popular type of lottery tickets is the so-called scratchable lottery ticket, in which a number of discrete areas of the ticket are covered with a latex or similar material that covers underlying symbols, numbers or icon-like drawings. An example of such a scratchable lottery ticket is shown at reference numeral 100 in FIG. 1. In such a typical lottery ticket, the buyer scratches the latex covering layers 110 from all or only a few such areas, to reveal the underlying symbols, numbers or icons. In such tickets, winning is often achieved by matching a number of such symbols, by spelling a given word, or by completing a sequence. An example of a scratchable lottery ticket in which a plurality of latex areas has been scratched off is shown at 200 in FIG. 2. For example, by scratching off five latex covered areas and matching three of the underlying symbols, numbers or icons, the buyer wins a free ticket, a prize or a predetermined cash sum. In FIG. 2, two icons are shown within the areas identified by reference numerals 220 and 230. In this manner, by scratching off the latex covering from five areas and matching the dollar bill icons shown in areas 220 three times, the buyer may redeem his or her lottery ticket for a predetermined cash payment.
A great many such tickets are sold annually. To determine whether a given lottery ticket is a winning ticket, therefore, requires countless hours from the cashiers, store employees and the like who must closely examine the ticket and make the appropriate decisions. It is thus desirable to automate this process. Moreover, lottery ticket fraud is sometimes difficult to detect. For example, some latex covered areas may have been partially scratched off and re-covered, without the knowledge of the store owner or the person that is charged with making the determination as to whether a particular ticket is a winning lottery ticket.
A variety of security measures and systems for automating the reading of such tickets have been adopted. For example, conductive ink patterns have recently been added to the latex-covered areas. The conductive ink patterns can assume various shapes or follow elaborate fine patterns similar to those found in high-density printed circuits. Such ink patterns, by their conductive nature, allow the presence, integrity and uniformity of the latex layer to be determined using electro-mechanical sensing means. Capacitive sensors have been utilized for that purpose. For example, a scratchable lottery ticket may be inserted in an appropriate sensing device. As the ticket travels past a number of transmitting and receiving electrodes separated by a shielding electrode, the coupling capacitances between transmitting and receiving electrodes will be different depending on whether the latex layer has been scratched off or not. This is because electric charges accumulate on the conductive ink patterns applied to the latex as the ticket passes under the electrodes. When such conductive ink patterns are no longer present or have been fraudulently altered, or when their corresponding latex layers have been partially or completely scratched off, the coupling capacitances between transmitting and receiving electrodes will differ from a baseline capacitance established when the latex layer and conductive ink patterns are intact.
By correlating the sensed capacitances with their spatial position on the lottery ticket, it is possible to determine which of the latex layers have been altered or scratched off, by analysis of their electrical signatures. However, this capacitive sensing method suffers from a number of drawbacks that limit its effectiveness and functionality. Chief among these is the sensitivity of such a capacitive sensor to distance variations between the conductive ink pattern and the sensing electrodes. As such lottery tickets have often been extensively and rather indelicately handled by the consumer, they may have become deformed or bent. As the lottery tickets are introduced into the capacitive sensor device, bends, creases and other non-uniform features may adversely affect the capacitive coupling between the transmitting and receiving electrodes, and thus the reliability of the reading. Other sources of distance variations are misalignment of the sensors within the sensor device itself. Such a misalignment may also cause erroneous readings.
The precise distance requirement between the conductive ink pattern and the sensing electrodes also implies that a predetermined amount of pressure must be applied between the capacitive sensor and the paper media to insure uniformity of the readings. This makes it difficult to integrate such capacitive scanning techniques in tandem with other scanning techniques, such as optical image sensing. This pressure also makes it difficult to advance the ticket through the sensor at high speeds without damage thereto.
Moreover, capacitive coupling sensitivity to distance and misalignment requires large electrode plates and therefore inherently limits this technique's ability to resolve small patterns. What is needed, therefore, is a method and apparatus to electro-mechanically read such scratchable lottery tickets that is less sensitive to distance variations occasioned by bends and creases in the lottery tickets, as well as by misalignment of the sensors.
What is also needed is a method and an apparatus to more reliably and accurately read such scratchable lottery tickets by sensing and analyzing the electrical signatures of the conductive ink patterns applied to the latex covered areas of the tickets.
Furthermore, what are also needed are a method and an apparatus capable of being readily scaled down to resolve ever finer and increasingly dense conductive ink patterns, to deter fraud.
What is also needed is a non-contact sensing method that is readily applicable to high-speed scanners.